Referring to the God of Judaism and Islam, which conceivably defines monotheism, why would God have a name?
If there is only One God, does "THE GOD" need a name? A proper name? Is it a sociological aspect of humans wanting to anthropomorphise God? Or does God really have a proper name? If so, what for?
Put yourself in God's position. Lets say that you create a miraculous universe, replete with intelligent creatures, and you make it beautiful with natural wonders. Then what? Do you make such a fine life for creatures then not ask expect a certain minimal amount of gratitude?
From time to time, God instructs mankind, and he expects that they will heed his words (don't kill....don't make wars, for example). God gets deeply depressed when he sees people openly defying him....take the recent war in Iraq, for example.
So, from time to time, God demands that we read what he commanded, open what he commanded, and respect him, and not worship others (otherwise we would follow what they command and ignore God's commandments which are designed to keep us safe and happy).
So,
God demands that we honor him and think of him.
To do so, usually requires a name.
Some fear to speak the name of God, for fear of repercussions. So they say G-d instead. Archie Bunker (TV show) used to point to God, but put his hand over his pointing finger so God wouldn't see it. God sees and hears all, of course, even that which is not said.